1. Distributed Temperature Sensing: A Transformative Technology in Water Resources Scott W. Tyler University of Nevada, Reno Dept. of Geologic Sciences and Engineering styler@unr.edu http://wolfweb.unr.edu/homepage/tylers/index.html/

2. What is Distributed Temperature Sensing (DTS) The measurement of temperature (and) using only the properties of a fiber-optic cable. The measurement of temperature (and) using only the properties of a fiber-optic cable. The fiber-optic cable serves as the thermometer, with a laser serving as the illumination source. The fiber-optic cable serves as the thermometer, with a laser serving as the illumination source. Measurements of temperature every 1-2 meters for as long as 30 km can be resolved, every 1-60 minutes, with temperature resolution of 0.01- 0.5 o C. Measurements of temperature every 1-2 meters for as long as 30 km can be resolved, every 1-60 minutes, with temperature resolution of 0.01- 0.5 o C. Spatial location of temperature is resolved identically to Time Domain Reflectometry Spatial location of temperature is resolved identically to Time Domain Reflectometry

3. Optical Fiber – Basic Construction ΘaΘa Lower Refractive Index Higher Refractive Index Core Cladding Θ a = Acceptance Angle Total Internal Reflection

4. Raman Scattering for Temperature Thermal energy drives oscillations within the lattice of the doped amorphous glass making up the fiber. Thermal energy drives oscillations within the lattice of the doped amorphous glass making up the fiber. When excited by photons (from the laser illumination), the interactions between the photons and the electrons of the solid occurs, and results in light being scattered (re-emitted) and shifted to higher and lower frequencies When excited by photons (from the laser illumination), the interactions between the photons and the electrons of the solid occurs, and results in light being scattered (re-emitted) and shifted to higher and lower frequencies The scattered light is shifted in frequency equivalent to the resonant frequency of the oscillating lattice ( a constant for any particular molecular structure) The scattered light is shifted in frequency equivalent to the resonant frequency of the oscillating lattice ( a constant for any particular molecular structure) Higher intensity of thermal oscillation produces higher intensities of the scattered light. Higher intensity of thermal oscillation produces higher intensities of the scattered light.

5. Distributed Temperature Sensing Anti-Stokes Stokes shifts with temperature Brillouin in frequency Raman (Anti-Stokes) in amplitude Rayleigh Scattering Brillouin Raman (Stokes) Frequency Amplitude/ Intensity Tyler, et al., J Glaciology, 2008

6. Currently used in fire monitoring, oil pipeline monitoring, high tension electrical transmission cables, down hole monitoring of oil production, dam seepage. Detector serves as both OTDR (for distance) and intensity (for Stokes and anti-Stokes) Figure courtesy of AP Sensing.

7. Advantages of DTS The cable serves as the measuring device The cable serves as the measuring device Fiber optic cable is relatively inexpensive ($0.50- $10/meter) and robust and have small thermal inertia. Fiber optic cable is relatively inexpensive ($0.50- $10/meter) and robust and have small thermal inertia. Once installed, continuous measurements do NOT disturb the fluid column (wells) or soils. Once installed, continuous measurements do NOT disturb the fluid column (wells) or soils. Very high resolution and long cables can provide high density coverage of a landscape, lake, or groundwater reservoir. Very high resolution and long cables can provide high density coverage of a landscape, lake, or groundwater reservoir. Installations can be temporary or permanent. Installations can be temporary or permanent.

8. Example Applications Example Applications Snow dynamics (Dozier, McNamara, Burak, Selker) Snow dynamics (Dozier, McNamara, Burak, Selker) Measuring mixing in the thermocline of Lake Tahoe (Selker, Schladow Torgersen and Hausner Measuring mixing in the thermocline of Lake Tahoe (Selker, Schladow Torgersen and Hausner Towards developing integrated soil moisture at large spatial scales (Selker, Miller, Hatch) Towards developing integrated soil moisture at large spatial scales (Selker, Miller, Hatch) Cave air circulation (Wilson, Barber and Jorgensen) Cave air circulation (Wilson, Barber and Jorgensen) Stream/Groundwater Exchanges (Conklin, Bales, Hopmans) Stream/Groundwater Exchanges (Conklin, Bales, Hopmans)

9. Challenges of Snow Installations Cold Temperatures; Freeze/Thaw common Cold Temperatures; Freeze/Thaw common Rodents/Burrowing animals Rodents/Burrowing animals Lack of access throughout winter Lack of access throughout winter Significant strains possible due to creep, consolidation, metamorphosis and avalanche Significant strains possible due to creep, consolidation, metamorphosis and avalanche Small thermal gradients need to be resolved Small thermal gradients need to be resolved Solar heating on fiber, particularly in late stages of melt when snow is dominated by ice may affect observed temperatures Solar heating on fiber, particularly in late stages of melt when snow is dominated by ice may affect observed temperatures

10. Mammoth Mountain Ski Area (Sierra Nevada)

12. Typical DTS Signals Cable loss Stokes/Anti Stokes

13. Bare Ground vs. Buried Cable Note Scale Difference Below Snow From Tyler et al., 2008 Diurnal variations clearly define bare and snow covered areas

14. Lake Tahoe, CA Test Site

15. Cable Deployment Cables were deployed from the UC Davis research vessel John LeConte Cables were deployed from the UC Davis research vessel John LeConte Cable was lowered to the bottom of the lake, then pulled up 20 m Cable was lowered to the bottom of the lake, then pulled up 20 m Total depth was approximately 411 m. Total depth was approximately 411 m.

16. Weather Conditions: June 6 The previous day was very cold and windy The previous day was very cold and windy Strong westerly's Strong westerly's

17. Weather Conditions: June 7 Warm, calm day Warm, calm day Smooth water Smooth water

18. Complete Vertical Profile: Single Ended

19. Note the wavy pattern of the warm water interface! Causing mixing of nutrients to the bottom waters From Tyler et al., 2008 Detailed View of the Thermocline at ~40 meters

20. Measurement of Soil Moisture during Irrigated Agriculture We can measure soil moisture only in the very uppermost portions of the soil with radar, but few methods are available to measure spatially distributed soil moisture IN the root zone! We can measure soil moisture only in the very uppermost portions of the soil with radar, but few methods are available to measure spatially distributed soil moisture IN the root zone! Here, we use a passive approach, relying upon solar heating and time lag at 15 cm, τ, to estimate the soil thermal diffusivity every 1 meter along the cable. Here, we use a passive approach, relying upon solar heating and time lag at 15 cm, τ, to estimate the soil thermal diffusivity every 1 meter along the cable. τ (x, y, t) = f(thermal diffusivity, depth, x, y) τ (x, y, t) = f(thermal diffusivity, depth, x, y) τ (t) = f(thermal diffusivity) ~ f(θ) τ (t) = f(thermal diffusivity) ~ f(θ) Active methods, in which a heater cable provides the input have also been developed at OSU and LBL and are analogous to heat dissipation sensors. Active methods, in which a heater cable provides the input have also been developed at OSU and LBL and are analogous to heat dissipation sensors.

21. Installing fiber optic cable 1000m of armored cable installed at 15cm depth 1000m of armored cable installed at 15cm depth Dragged and seeded Dragged and seeded

23. Temperature vs. Time Time Air Temperature (ºC) 30 25 20 15 10 35 30 25 20 15 Soil Temperature (ºC) 7/26 7/27 7/28  = 7% K T ~ 30 cm 2 /hr soil temperature air temperature ∆t DRY SOIL

24. Soil Moisture (%) - symbols 25 20 15 10 5 7/267/27 7/287/29 Thermal Diffusivity (cm 2 /hr) - lines 100 80 60 40 20 irrigation event irrigation event drying DRY SOIL Soil Moisture & Thermal Diffusivity

25. Measuring Air Flow in Carlsbad Caverns Nat. Park Air circulation in CCNP an important aspect of cave biology and cave management Air circulation in CCNP an important aspect of cave biology and cave management Air circulation and thermal convection is believed to control many cave feature formation processes. Air circulation and thermal convection is believed to control many cave feature formation processes. Air circulation may be an analog to fluid convection during cave formation. Hot, saline fluids believed to be dominant cave forming mechanism. Air circulation may be an analog to fluid convection during cave formation. Hot, saline fluids believed to be dominant cave forming mechanism.

27. Cave Air Temperatures Cave Entrance Wet Area

28. VERTICAL THERMAL PROFILES IN A TALL (>30 m ) ROOM WELL MIXED LOWER ROOM STRATIFIED UPPER ROOM

29. Stream/Meadow Monitoring Sequoia National Park

30. Stream Temperature Profile Ice Bath Meadow Deep Pools and Stream

31. Conclusions and Vision DTS can provide fundamental insights into exchange processes and thermal stratification (Tahoe gravity waves, cave circulation, diurnal variations in stream “dead-zone” volumes). DTS can provide fundamental insights into exchange processes and thermal stratification (Tahoe gravity waves, cave circulation, diurnal variations in stream “dead-zone” volumes). Data “granularity” allows us to probe small scale processes, while at the same time measuring across broad spatial scales (snow monitoring, soil moisture measurement) Data “granularity” allows us to probe small scale processes, while at the same time measuring across broad spatial scales (snow monitoring, soil moisture measurement) CUAHSI/NSF-sponsored workshops in 2007 and 2008 have trained ~70 professionals and students, and also shaped our views on technology transfer. Another planned for July 2009 in Denmark. CUAHSI/NSF-sponsored workshops in 2007 and 2008 have trained ~70 professionals and students, and also shaped our views on technology transfer. Another planned for July 2009 in Denmark. Other applications on-going Other applications on-going Borehole logging and fracture flow, ASR Borehole logging and fracture flow, ASR Monitoring prescribed fire soil temperatures Monitoring prescribed fire soil temperatures Lake/atmosphere exchange and evaporation from lakes Lake/atmosphere exchange and evaporation from lakes Vertical snow temperature monitoring Vertical snow temperature monitoring Stream/fish habitat recovery, both for cold water species (salmon) and thermophiles (Devils Hole pupfish) Stream/fish habitat recovery, both for cold water species (salmon) and thermophiles (Devils Hole pupfish) Monitoring solar inputs to aquatic systems. Monitoring solar inputs to aquatic systems.